1. Field of the Invention
The present invention relates to a range sensing apparatus of an automatic transmission.
2. Description of Related Art
A range sensing apparatus, which senses a shift range of an automatic transmission, is known. For instance, in a range sensing apparatus recited in Japanese Unexamined Patent Publication No. 2002-175744A or Japanese Unexamined Patent Publication No. 2006-118643A (corresponding to US2006/0093169A1), the shift range of the automatic transmission is sensed with a sensor, which is provided in a housing, based on a moving position (operational position) of a slider, which is driven to reciprocate along guide rails of a housing in response to the selection of the shift range.
The range sensing apparatus recited in Japanese Unexamined Patent Publication No. 2002-175744A or Japanese Unexamined Patent Publication No. 2006-118643A (corresponding to US2006/0093169A1) is placed in a transmission case, in which hydraulic fluid (oil) of the automatic transmission is sprayed. Therefore, the hydraulic fluid of the automatic transmission, which flows downward to the range sensing apparatus, may enter into a movable range of the slider. The hydraulic fluid of the automatic transmission may possibly contain foreign objects (e.g., debris left at the time of forming a component of the automatic transmission or metal powder generated through frictional wearing of the component). When the hydraulic fluid of the automatic transmission, which contains the foreign objects, adheres to a sliding surface of the slider, malfunction of the slider and thereby malfunction of the range sensing apparatus may occur.
In the range sensing apparatus recited in Japanese Unexamined Patent Publication No. 2002-175744A, the sensor, which senses the shift range, is provided to a wall surface of a vertical wall. Therefore, an input shaft, which is connected to the slider that is movable in a horizontal direction along the vertical wall, projects in the horizontal direction, which is perpendicular to the wall surface of the vertical wall. Thus, a slit, through which the input shaft projects from the housing, is formed in the housing such that an opening of the slit extends in the horizontal direction. An upper peripheral edge of the opening of the slit projects further from a lower peripheral edge of the opening of the slit toward the outside of the housing. Thereby, the hydraulic fluid, which is applied to the opening of the slit from the upper side of the opening of the slit, can be blocked by the upper edge of the opening of the slit to limit the intrusion of the hydraulic fluid into the movable range of the slider. In addition, holes, which communicate between an inside and the outside of the housing, are provided in a lower part and an end part, respectively, of the movable range of the slider in the housing. Thereby, the hydraulic fluid and foreign objects, which enter into the movable range of the slider, can be expelled to the outside of the housing through the holes upon the reciprocation of the slider.
In Japanese Unexamined Patent Publication No. 2006-118643A (corresponding to US2006/0093169A1), the sensor, which senses the moving position of the slider, is placed on the lower side of the slider and faces the upper side where the slider is located, and the slider is supported by the guide rails of the housing from the lower side of the slider. The downwardly moving hydraulic fluid and foreign objects may enter the movable range of the slider. However, due to the reciprocating movement of the slider, the hydraulic fluid and foreign objects are collected by a front end part of the slider, which is located on the front side in the moving direction of the slider. Then, the hydraulic fluid and foreign objects are expelled to the outside of the housing through holes, which are provided to the lower guide rail.
In the case of Japanese Unexamined Patent Publication No. 2002-175744A, the intrusion of the downwardly moving hydraulic fluid into the movable range of the slider can be limited. However, the hydraulic fluid, which is applied from the lateral side, may not be sufficiently limited, and the expelling of the foreign objects through the holes, which are provided in the lower portion and the end portion, respectively, of the movable range of the slider in the housing, may not be sufficient in some cases depending on a size of the foreign objects. Furthermore, the projection of the upper edge of the opening of the slit may be implemented by providing a separate cover to the upper edge of the opening of the slit or by bending the upper edge of the opening of the slit. However, this will result in an increase in the number of the components or an increase in the processing costs.
When a large quantity of the hydraulic fluid and foreign objects move downward in the case of Japanese Unexamined Patent Publication No. 2006-118643A (corresponding to US2006/0093169A1), it may possibly result in a sliding malfunction of the slider. Also, a sufficiently effective expelling of the foreign objects may not be achieved unless providing a sufficiently large size of the holes, through which the foreign objects are expelled. In addition, in the case where the multiple holes are formed in the guide rail, it will require a complicated process, so that the manufacturing costs may be disadvantageously increased.